1. Field of the Invention
The present invention relates to mobile communication systems, mobile communication methods, base stations, and mobile stations and, more particularly, to a mobile communication system comprising a mobile station and a base station equipped with a plurality of antennas and configured to perform signal transmission/reception control including signal retransmission control by the base station on the basis of an automatic repeat request from the mobile station, a mobile communication method executed by the mobile communication system, and the base station and the mobile station constituting the mobile communication system.
The present invention also relates to signal transmitting methods and systems in mobile communication systems and, more particularly, to a signal transmitting method and system in a mobile communication system configured to perform transmission/reception of a signal while transmitting and receiving an automatic repeat request, the signal transmitting method and system being configured to transmit the signal while changing channels one from another so as to improve the receiving quality at the mobile station.
Further, the present invention relates to base stations that can perform communication according to the aforementioned signal transmitting methods.
The present invention also relates to mobile stations performing communication according to the foregoing signal transmitting methods.
2. Related Background Art
FIG. 1 is a block diagram of a conventional mobile communication system 10, and FIG. 2 a chart for explaining the cooperative operation of the conventional mobile communication system with an automatic repeat request. At a base station 1, an ARQ (Automatic Repeat Request) processor 2 accepts input data addressed to a mobile station 11 through a data input terminal 6. The ARQ processor 2 attaches error-detectable parity such as CRC (Cyclic Redundancy Checking code) or the like to the data so as to enable detection of an error occurring during transmission, thereafter stores the data (A1 in FIG. 2), and outputs the data to a transmitter 3. The transmitter 3 modulates the input data into a transmitted signal and then transmits the signal through a transmitted/received wave splitter 4 and from a first base station antenna 7 to the mobile station 11 through a downlink 22 (A2).
At the mobile station 11, a receiver 12 receives the signal from a mobile station antenna 17 through a transmitted/received wave splitter 16. Then the signal received at the receiver 12 is fed as received data to an ARQ processor 13 (A3). The ARQ processor 13 performs detection of error using the CRC (A4).
When no error is detected in the received data herein, the ARQ processor 13 outputs the received data from a data output terminal 14 and outputs an acknowledgement of arrival of the received data to a transmitter 15. The transmitter 15 transmits the acknowledgement of arrival of the received data to the ARQ processor 2 of the base station 1 through an uplink 21 (A5). Receiving the arrival acknowledgement, the ARQ processor 2 deletes the data stored for retransmission (A7 and A8).
When an error is detected in the received data at A4 on the other hand, the ARQ processor 13 sends a repeat request for retransmission of the received data to the ARQ processor 2 of the base station 1 through the uplink 21 (A6). Receiving the repeat request, the ARQ processor 2 retransmits the requested data from the first base station antenna 7 (A7 and A9).
FIG. 3 and FIG. 4 are a block diagram of another conventional mobile communication system and a flowchart for explaining the operation thereof. As shown in FIG. 3, the conventional mobile communication system is comprised of a base station 21 and a mobile station 31.
The base station 21 is generally comprised of an ARQ (Automatic Repeat Request) processor 22, a transmitter/receiver 23, a signal input terminal 24, and a base station antenna 25. The mobile station 31 on the other hand is generally comprised of a transmitter/receiver 32, an ARQ processor 33, a signal output terminal 34, and a mobile station antenna 35.
The operation of the conventional mobile communication system will be described below with reference to the flowchart of FIG. 4.
At the base station 21, the ARQ processor 22 receives an input signal addressed to the mobile station 31 through the signal input terminal 24. The ARQ processor 22 attaches the error-detectable parity such as the CRC (Cyclic Redundancy Checking code) or the like to the data so as to enable detection of an error occurring during transmission, thereafter stores the signal (B1), and outputs the signal to the transmitter/receiver 23. The transmitter/receiver 23 informs the mobile station of a start of transmission of the signal (B2) and thereafter transmits the signal to the mobile station 31 through a downlink 42 which is a frequency channel determined for transmission of the signal addressed to the mobile station (B3).
At the mobile station 31, the transmitter/receiver 32 receives the signal of the downlink 42 received by the mobile station antenna 35 (B4) and thereafter the signal is fed into the ARQ processor 33. The ARQ processor 33 performs the detection of error in the received signal, using the CRC. When no error is detected in the received signal (NO at B5), the received signal is outputted from the signal output terminal 34 and an acknowledgement of arrival of the received signal is transmitted to the ARQ processor 22 of the base station through an uplink 41 (B6) After that, the ARQ processor 22 receiving the arrival acknowledgement deletes the signal stored for retransmission (NO at B8, and B9).
When an error is detected in the received signal on the other hand (YES at B5), the ARQ processor 33 sends a repeat request for retransmission of the received signal to the ARQ processor 22 of the base station through the uplink 41 (B7). Then the ARQ processor 22 receiving the repeat request retransmits the requested signal in the frequency channel used for the preceding transmission (YES at B8, and B10).